The invention generally relates to a sealing mechanism for a subterranean well.
For such purposes as producing fluid from and testing a subterranean well, a device called a packer may be used. The packer typically is run downhole on a tubular string. The packer, when set, forms an annular barrier in a region (typically called the “annulus”) between the string and a wellbore wall or a casing wall, depending on whether the well is cased.
A typical packer includes an annular elastomer sealing ring that is exposed on the outside of the packer and is concentric with the longitudinal axis of the string. When run downhole, the elastomer ring is uncompressed, a state that minimizes the outer diameter of the ring. When the packer is to be set, sleeves (hydraulically or mechanically activated sleeves, for example) compress the elastomer sealing ring so that the ring radially expands to seal off the annulus.
The above-described conventional packer typically is optimized to form a seal between a string and the inside of a casing wall. However, challenges may arise in sealing off the annulus in an uncased well. More specifically, the wellbore wall that defines the surface to which a seal must be formed typically has an irregular profile, and the elastomer sealing ring typically has a relatively uniform radius of expansion. Therefore, it may be challenging to form a seal between the elastomer sealing ring and an irregularly-shaped borehole wall.
Thus, there is a continuing need for better ways to seal off the annulus in an uncased well. There is also a continuing need for better ways to seal off the annulus in a cased well.